In the use of office printers, there is a need for sheet receiving apparatus which is capable of segregating the output in categories involving set separation of multiple copies, job separation of multiple jobs and user or recipient separation, particularly in the case of networked printers.
Such devices are commonly referred to as mailboxes or random access sorting machines in which the printed material is not necessarily directed into successive trays as in the typical sorting or collating machines employed, say with office copiers.
Random access sorting devices useful as mailboxes may take various forms. For example, in U.S. Pat. Nos. 4,691,914 and 3,937,459 there are disclosed forms of such sorters which may be used in conjunction with a copying machine in a sorting or collating mode in which successive sheets of copy from the copier are deflected from a sheet transport into successive trays of a vertically spaced set of trays. Such sorters are also useful as job separators when used in a job separation mode, as well as being useful as random access sorters or mailboxes because the sheet deflectors may be actuated at random, under the control of a printer.
Another type of random access sorter, as exemplified in U.S. Pat. No. 4,843,434, may also be operated to receive sheets from a copier for sequentially collating the copies or separating jobs. However, inherently, such sorters are not truly random access in their operating mode because the sheet deflector which travels sequentially in a normal collating operation in association with a copier must also be moved sequentially from tray to tray when operating as a random access mailbox. Such sequential tray to tray movement of a deflector or an actuator, therefore, is not well suited for use in mailboxing in the case that the printer operates at such a speed as to afford only a short inter-document gap between successive sheets and the deflector must move from one selected tray to another tray, at random, during the period permitted by the rate of travel of successive sheets. In the alternative, the production rate of the printer may be compromised to afford adequate time intervals between sheets to enable shifting of the sheet deflector, but impedance of the copier feed rate is objectionable.
With the foregoing in mind it is clear that, particularly in the case of printers which operate at speeds of, say, 15 plus pages per minute, the preferred form of receiver or mailbox is of the fixed bin type with deflectors at each tray that can be actuated to and from the positions forming part of the sheet path for deflecting sheets from the sheet path into the associated tray, because operation of the deflector can be instantaneous, as by means of a solenoid, as disclosed in the aforementioned U.S. Pat. No. 4,691,914.
U.S. patent application Ser. No. 849,223, filed Mar. 10, 1992, now U.S. Pat. No. 5,328,170, and co-owned herewith, discloses an actuator for gate type sorters which operates uni-directionally to mechanically open gates for random access to the trays. However, here again, there is a period of time required between sheets necessary to allow movement up or down of the actuator to position it for actuation of a particular or selected gate.
In U.S. patent application Ser. No. 044,439, filed Mar. 29, 1993, now U.S. Pat. No. 5,344,131, and co-owned herewith, there is disclosed a random access sorter or mailbox which utilizes features of U.S. Pat. Nos. 3,937,459 and 4,691,914 to utilize paper controlling feed rollers and compact gate devices in a relatively short assembly for a given number of trays of a given maximum sheet capacity per tray.
Another problem involved in the practical application of mailboxing sheet receivers to the modern office printers involves size and expense. As laser printer technology has evolved, the size and cost of printers have both been reduced, so that the cost of a mailbox, as compared with the cost of a host printer has become more of a problem, as has the aesthetic balance of the mailbox and printer, because incorporation of the preferred, fixed bin, random access technology in an inexpensive and small package is a difficult task, due to the inherent number of parts and operating mechanisms and the vertical space occupied by, say, up to twenty bins, combined with a stacker for output which does not require mailboxing or even sorting.
In order to avoid excessive height, it has heretofore been known to duplex sorter devices to double the capacity, either by bypassing the printer output from a first sorter to a second sorter in a horizontally spaced pair, or mounting a pair of sorters in back to back relation. However, doubling the capacity in such ways more than doubles the cost because of the need for selective feeding of sheets to one or the other of the two sorter assemblies.